Magnetic resonance imaging (MRI) was safe in patients who had a legacy pacemaker or a legacy implantable cardioverter-defibrillator system, a recent study found. The prospective, nonrandomized study assessed the safety of MRI at a magnetic field strength of 1.5 Tesla in 1,509 patients who had a pacemaker (58%) or an implantable cardioverter-defibrillator (42%) that was not considered to be MRI-conditional. Overall, patients underwent 2,103 thoracic and nonthoracic MRI examinations that were deemed as clinically necessary. Researchers found:

No long-term clinically significant adverse events were reported.

The most common notable change in device parameters immediately after MRI was a decrease in P-wave amplitude (in 1% of patients).

At long-term follow-up, the most common notable changes from baseline were decreases in P-wave amplitude (in 4% of patients), increases in atrial capture threshold (4%), and increases in left ventricular capture threshold (3%).

The observed changes were not clinically significant, however, and did not require revision or reprogramming.

People with cardiac pacemakers or ICDs often need MRIs, but are unable to get the MRI due to concern about the MRI interfering with the function of the pacemaker. This study shows that MRIs can be done in this group of patients. It is important to be aware that the patients did not just get an MRI without any input from the cardiologist. To avoid problems with electromagnetic interference causing inappropriate pacing, a specific protocol was used for all patients getting the MRIs. Asynchronous pacing mode were programmed, for instance, for pacing-dependent patients to avoid inappropriate inhibition of pacing. Other pacing modes were used for patients without pacing dependence. For patients whose devices were set to detect tachyarrhythmias, the devices were deactivated to avoid delivery of unneeded pacing or shocks. The main takeaway point of this article is that MRIs can be done in patients with pacers and ICDs, as long as appropriate expert consultation is available to manage the pacer settings and there is availability if needed of external pacing. — Neil Skolnik, MD